User profile for user: Ben Low
Ben Low Author
User level: Level 1
112 points

Deleting APFS snapshots? Dangerous?

I realise this is not directly an FCPX question, but it is tangentially related and the team here is so smart ... and I'm wondering if someone has come across something like this?


I've got a Thunderblade RAID setup running = 32 TB's SSD. I deleted 4 TB's of data to free up space several months ago. But neither the Finder window, nor the SoftRAID, nor the 'Get Info' show that this space has been freed up. And the data I deleted (a film project) is no longer on the Thunderblade RAID setup. So the available space should have changed.


I know APFS snapshots can get weird, or not refresh, or take their time refreshing. But this has been a couple of months. I need to finish this film, meaning I need to add more media. And I don't want to risk overloading the RAID volume.


Can I simply 'delete' the APFS snapshots (in Disk Utility) and then Apple will rebuild them? And maybe fix the mis-read? Or by deleting the APFS snapshots will I be destroying everything on the Thunderblade RAID setup? And all my precious work.


I've been working with OWC Tech support on this. They say it is an issue. They say that often the SoftRaid doesn't see the change, but if I click the Thunderblade volume icon on the desktop and 'Get Info' it will show the accurate reading. Only this isn't happening in my case.


Any ideas? I'm all ears ... Ben

MacBook Pro (2017 – 2020)

Posted on May 2, 2023 10:32 AM

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User profile for user: Davis_
Davis_
User level: Level 2
219 points

Posted on May 2, 2023 11:22 AM

(Take note: No guarantees about the provided info...)


Ben, I usually delete Time Machine snapshots before I do any macOS update/upgrade (in Disk Utility). I do it booted in Recovery Mode.


APFS Snapshots for Time Machine are likely different (in purpose) than the "volume" snapshots for your Thunderblade. Snapshots store changes for an entire volume and usually successive numbered snapshots are just changes to the previous snapshot (back to the original). Snapshots typically (in your case) would store deleted files for some (supposedly short) period of time before permanently removing the files. If SoftRAID wasn't part of the equation, I'd say go ahead and remove the snapshots (after rebooting into Safe Mode once).


However, with SoftRAID, things get more complicated. In fact, without SoftRAID, the volume's snapshots may have been processed (deleted) before you might have noticed anything. It may be that SoftRAID caused those snapshots to be made (certain applications, etc., _can_ create snapshots), in which case SoftRAID seems buggy in that it didn't process those snapshots in a timely manner. I use SoftRAID myself, but only on a multi HDD setup (HFS+ Journaled, not APFS).


If you want to proceed, I'd suggest backing up the contents on the Thunderblade first. Run "First Aid" on the volume in Disk Utility, do a Safe Mode boot cycle, and then try removing the snapshots while in Recovery mode. This may not work if the SoftRAID driver isn't loaded when your Mac is in Recovery Mode. If so, you'd have to do it after a normal boot.


Here's a pretty clear explanation of APFS snapshots you should read, regardless of what you do:


https://eclecticlight.co/2022/02/10/managing-snapshots-how-to-stop-them-eating-free-space/


I'd recommend reading all of the article comments, as well.



Cheers.


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User profile for user: Davis_
Davis_
User level: Level 2
219 points

May 2, 2023 11:22 AM in response to Ben Low

(Take note: No guarantees about the provided info...)


Ben, I usually delete Time Machine snapshots before I do any macOS update/upgrade (in Disk Utility). I do it booted in Recovery Mode.


APFS Snapshots for Time Machine are likely different (in purpose) than the "volume" snapshots for your Thunderblade. Snapshots store changes for an entire volume and usually successive numbered snapshots are just changes to the previous snapshot (back to the original). Snapshots typically (in your case) would store deleted files for some (supposedly short) period of time before permanently removing the files. If SoftRAID wasn't part of the equation, I'd say go ahead and remove the snapshots (after rebooting into Safe Mode once).


However, with SoftRAID, things get more complicated. In fact, without SoftRAID, the volume's snapshots may have been processed (deleted) before you might have noticed anything. It may be that SoftRAID caused those snapshots to be made (certain applications, etc., _can_ create snapshots), in which case SoftRAID seems buggy in that it didn't process those snapshots in a timely manner. I use SoftRAID myself, but only on a multi HDD setup (HFS+ Journaled, not APFS).


If you want to proceed, I'd suggest backing up the contents on the Thunderblade first. Run "First Aid" on the volume in Disk Utility, do a Safe Mode boot cycle, and then try removing the snapshots while in Recovery mode. This may not work if the SoftRAID driver isn't loaded when your Mac is in Recovery Mode. If so, you'd have to do it after a normal boot.


Here's a pretty clear explanation of APFS snapshots you should read, regardless of what you do:


https://eclecticlight.co/2022/02/10/managing-snapshots-how-to-stop-them-eating-free-space/


I'd recommend reading all of the article comments, as well.



Cheers.


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User profile for user: Ben Low
Ben Low Author
User level: Level 1
112 points

May 3, 2023 5:19 PM in response to Davis_

Hi Davis_


Finally I backed up the Thunderblades to a Thunderbay ... then went into Disk Utility and basically deleted all the APFS snapshots. Poof. Then I went back to the Thunderblades and in a minute or two, sure enough, I had 9.15 TB's of free space opened up.


And trashing the APFS snapshots didn't seem to have any negative effect on the Thunderblades. Touch wood.


Thank you kindly for your help, very much appreciated.


Ben

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Deleting APFS snapshots? Dangerous?

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